linux-kernel - Re: [PATCH] mmc: Add new via-sdmmc host controller driver

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Message-ID: <20090614125537.065d706a@mjolnir.ossman.eu>
Date:	Sun, 14 Jun 2009 12:55:37 +0200
From:	Pierre Ossman <pierre@...man.eu>
To:	Harald Welte <HaraldWelte@...tech.com>
Cc:	Linux Kernel Mailinglist <linux-kernel@...r.kernel.org>,
	JosephChan@....com.tw, Bruce Chang <BruceChang@....com.tw>
Subject: Re: [PATCH] mmc: Add new via-sdmmc host controller driver

On Sun, 14 Jun 2009 14:52:56 +0800
Harald Welte <HaraldWelte@...tech.com> wrote:

> > 
> > You need to do the removal as the first step 
> 
> Thanks, I've fixed this in my tree. 
> 
> Looking at other drivers, imxmmc seems to get this wrong, too.
> 

Quite right. I suppose someone should have a look at that...

> > and you might need to explicitly kill any ongoing requests.
> 
> you mean something like the snippet in sdhci.c:
> ======
>        if (dead) {
>                 spin_lock_irqsave(&host->lock, flags);
> 
>                 host->flags |= SDHCI_DEVICE_DEAD;
> 
>                 if (host->mrq) {
>                         printk(KERN_ERR "%s: Controller removed during "
>                                 " transfer!\n", mmc_hostname(host->mmc));
> 
>                         host->mrq->cmd->error = -ENOMEDIUM;
>                         tasklet_schedule(&host->finish_tasklet);
>                 }
> 
>                 spin_unlock_irqrestore(&host->lock, flags);
>         }
> ======
> 
> Why is sdhci about the only driver that does it?  What decides if we need
> to kill ongoing requests or not?
> 

I guess I haven't kept an eye on it so the others are simply buggy.

> Also, you stated that mmc_remove_host needs to be the first step.  However,
> sdhci first kills the ongoing rquest (if "dead"), and then removes the host.
> 

Right, because the reason you need to end the request is that failure
to do so will wedge the MMC system and mmc_remove_host() will never
return.

Normally the requests will eventually be completed by interrupts coming
from the hardware, but if it got removed then that might not happen.

Rgds
-- 
     -- Pierre Ossman

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